The purpose of the PhosBan Reactor 550 is to force water through the media and upward from the bottom. This stops channeling and ensures that the water is distributed evenly throughout the media. The PhosBan 550 media reactor is perfect for "hang on the back" applications because of its low profile and integrated hanging bracket. Your preferred filtration media can be stored in the Phosban reactor. Excellent for HOB applications Contains a ball valve Excellent with Phosban Media; feed pump needed The PhosBan 150 can be hung on the rear of the aquarium or mounted underneath it. It includes a 1/2" barbed ball valve for flow control and barb hose fittings for 1/2" tubing. Any pump that uses 1/2" can be used with the Phosban 550.